These prior art grates, including the two part grates, as well as the one part grates, are not subjected to uniform thermal stress when in use. This is especially true of the one part grates, and the temperature variations and uneven thermal stresses produced are particularly a problem in refuse incinerators.
Due to the temperature variations in the grate, and the uneven thermal stresses produced, the surface of the rear portion of the grate typically shrinks; and particularly in the two part grates, the rear grate portion is lifted off of the grate support. This lifting process is amplified by the fact that the fastening bolt engages the bottom side of the rear grate part only and pulls the rear grate part downward. As a result of this lifting off, the grate comes into contact with the superposed grate. Increased wear occurs, and in extreme cases the stoker comes to a standstill.
Thus, in accordance with the present invention, means is provided for holding the front grate part downwardly against the grate support, and the front and rear grate parts have interengaging means thereon whereby the front grate part holds the rear grate part downwardly to the grate support. The structure of the present invention is such that the rear grate part is not subjected to a non-uniform downward pull, as in the prior art, and in the event of thermal shrinkage will not be lifted off of the grate support.
Moreover, the rear grate part of the invention rests at four points on the grate support, and if a thermal shrinkage occurs, will be bent uniformly downwardly as a result of the four point rest.
Additionally, cooling slots and openings are provided in the grate of the invention for flow of cooling air for reducing the temperature variations and thermal stresses in the grate.